Trehalose lipids are known glycolipids, which contain trehalose as the disaccharide moiety and exhibit surface-active properties. The trehalose lipids can be prepared by means of microorganisms, for example as is known from U.S. Pat. No. 4,286,660. According to this method, an aqueous nutrient solution is mixed in a bioreactor with n-alkanes having a C.sub.8 to C.sub.24 chain length or with crude oil and this mixture is inoculated with a microorganism. The growth is carried out with an aeration rate of 0.5 to 1.0 V/V/min and an agitation speed of 400 to 1200 rpm at a temperature of 30.degree. C. to 50.degree. C., wherein the pH of the liquid culture is maintained at 6.8 to 7.0 by the addition of aqueous ammonia. The growth is terminated by a temperature shock, i.e. short heating of the liquid culture at a temperature of 60.degree. C. The cell mass is separated from the culture suspension. The remaining aqueous phase can be used directly or can be worked up to isolate glycolipids by known methods, for example, by extraction with a suitable solvent which is evaporated from the extract after separation from the culture solution.
According to this known process, trehalose lipids of the general formulae given below are obtained using the microorganisms Nocardia rhodochrous or Mycobacterium phlei. ##STR1## The yields of the trehalose lipids from this process lie between 600 and 700 mg/l of aqueous phase isolated from the liquid culture.
Hitherto only those trehalose lipids have been regarded as non-ionic surface-active substances which are esterified by a fatty acid in the CH.sub.2 OH groups in the C.sub.6 position, so that the corresponding trehalose lipids have been called trehalose diesters.
These known trehalose lipids can be represented by the general formula ##STR2## wherein R.sub.1 and R.sub.2 can be the following radicals: ##STR3## with m=8 to 10 and n=18 to 21 or ##STR4## with m=20 to 22 and n=14 to 17.
These compounds, which are non-ionic surface-active substances, can be considered as diesters of trehalose. They were obtained by this process in yields of 600 to 700 mg/l of the nutrient solution.
In a publication by S. G. Batrakov et al in "Chemistry and Physics of Lipids", 29 (1981), pages 241 to 266, a new type of trehalose lipids was reported which can be isolated from the cell mass of the paraffin oxidizing bacterium Mycobacterium paraffinicum. In addition to the known di-fatty acid esters of trehalose, such as 6,6'-di-O-mycolyl-.alpha.,.alpha.-D-trehalose, 6-0-mycolyl-.alpha.,.alpha.-D-trehalose and 6,6'-di-0-acyl (C.sub.12 -C.sub.16)-.alpha.,.alpha.-D-trehalose, the compounds 6-0-mycolyl-6'-0-acyl (C.sub.12 -C.sub.16)-.alpha.,.alpha.-D-trehalose and 2octanyl-3,2'-di-0-decanoyl-6-0-succinoyl-.alpha.,.alpha.-D-trehalose were isolated and identified.
According to J. F. T. Spencer et al in "Canadian Journal of Chemistry" 39 (1961), page 846, the fermentation of Torulopsis bombicola produces sophorolipids of the general formula: ##STR5## in which R.sup.1 and R.sup.2 are H or ##STR6## group, R.sup.3 is H or a --CH.sub.3 group and R.sup.4 is a saturated or unsaturated C.sub.11 -C.sub.16 hydrocarbon radical. These sophorolipids are obtained in the lactone form as shown in equilibrium with free acids formed by hydrolysis of the lactone bond. These sophorolipids are thus partly diacetyl esters.
According to U.S. Pat. No. 4,276,377, a glycolipid. methyl ester with surface-active and waxy properties can be obtained if a hydrated sophorolipid obtained by fermentation of Torulopsis bombicola is mixed with certain ether-alcohols and water is distilled off from this mixture. Whereupon, the anhydrous system of sophorolipids and ether-alcohol will undergo a methanolysis and a methylation reaction with methanol in the presence of a strong acid. Thereby both acetyl groups are split off and the acid groups esterified with methanol. This ester no longer has any ester groups in the sophorose part of its molecule, but only a lower alkyl ester of a carboxylic acid group of the fatty acid forming the lipid part of the molecule. Since the hydroxyl groups of the sophorose part of this ester are free, this non-ionic surfactant exhibits a high surface activity, which can be modified by ester exchange of the alcoholic methyl ester group with other alcohols having longer carbon chains in the molecule.